The present invention relates to pressure seals and more particularly to deformable gasket seals for pressurized helium containment within the linear drive system of a cryogenic refrigerator.
Helium cryogenic refrigerators utilize a linear drive assembly in which gaseous helium undergoes substantial variations in pressure. Due to the small size of the helium atom, there are substantial problems in obtaining simple inexpensive methods of sealing pressurized helium within such a refrigerator.
The most common seals used in pressurized devices are O-rings and gaskets composed of elastomeric compounds. These seals are generally positioned within mating grooves in adjacent parts. When exposed to temperature and pressure excursions that frequently occur in cryogenic refrigerators such elastomeric seals degrade causing leakage and thus loss of efficiency or failure.
Existing helium cryogenic refrigerators have used indium or other soft metals as O-rings within mating grooves to contain pressurized helium. U.S. Pat. No. 4,418,918, for example, discloses the use of a deformable metal ring, preferably made of indium, that is plastically deformed by a triangular shaped anti-rotation ring. The anti-rotation ring is compressed into the indium ring forming a V-shaped groove, thereby sealing the junction between rotatably secured members of a cryogenic refrigerator. Indium absorbs and retains radiation making it unsuitable for applications with possible exposure to radiation sources.